When you're using this mod (https://mods.factorio.com/mod/blueprint-sandboxes) no character gets ported into it so visually and mechanically it's indistinguishable from when you enter the remote view (apart from the fact that some functions are unaccusable from RV and some are done slower like deconstruction).

With the border completely gone (thank god and thank you) it'd've been great to have an option for at least some minimal indication that you're in fact in RV tho I'm not sure what'd be the best. Maybe a toogle-able button on that quickbar for mods (if needed, I can assist with making an icon)? Or just GUI text "Remote view" in the down left corner (where character's ammo inventory is)?

There's an option to keep the top bar enabled, but I can see how that would be too large still.
I would also like to point out that the presence of the minimap can tell you if you're not in remote view, but if you have that turned off as well then I suppose it doesn't help either.
I can add a per-player setting to have some text on screen, honestly the top middle would probably be easiest.

I would also like to point out that the presence of the minimap can tell you if you're not in remote view

If you're zoomed in on the world from RV the minimap appears tho.

But I actually have found the way to tell them apart, the quickbar completely empties when you're in RV so ig that'll do, no changes needed.